Typically American tree and herb centre (5)
I believe the answer is:
'typically american' is the definition.
I know nothing about this answer so I can't judge whether this works.
'tree and herb centre' is the wordplay.
'tree' becomes 'elm' (elm tree is a kind of tree).
'and' means one lot of letters go next to another.
'centre' indicates the central letters.
The centre of 'herb' is 'er'.
'elm'+'er'='ELMER'
Can you help me to learn more?
(Other definitions for elmer that I've seen before include "name" , "Man" , "- - Gantry (book, film)" , "____ Rice, US dramatist" .)